Continuous filter



Feb.- 26, 1945.

1.. OLIVER ETAL CONTINUOUS FILTER Fild Oct. 8, 1945 s Sheets-Sheet 1INVENTOE'5 i5 PHIL/P J. MC GUIEE.

q FIETHUE w VETTHL 29 BY 6 ATTERNEY 1 E L. OLIVER ET AL CONTINUOUSFILTER 3 Sheets-Sheet 2 Filed 00L 8, 1943 INVENTOEj PH/L/P 1. MC'GU/EEEDWIN Ll 01.11 52 JAMEj E. fiLHL/GHTEE AETHUE VV- VETTHL BY ATTORNEYPatented Feb. 26, 1946 CONTINUOUS FILTER Edwin Letts Oliver, Piedmont,Philip J. McGuire, San Francisco, James E. Slaughter, Santa Cruz, andArthur W. Vettel, Watsonville,Calif.;

said Oliver and said McGuire assignors Oliver United FiltersIncorporated, Oakland, Calif., a corporation of Nevada; said Slaughterand said Vettel assignors to The Permanente Metals Corporation, Oakland,Calif a corporation of California I,

Application October 8, 1943, Serial No. 505,460 Y ,7 Claims. (01.210-199) This invention relates in general to industrial filters whereina filter cell travels in a predetermined path through a body of pulp orslurryto a, discharge station, a. layer of cake is deposited on thesurface of the filter cell as it passes through the body of pulp orslurry under the influence of an inwardly directed difierentialfiltering pressure, and the layer of cake so formedls dischargedfromsaid cell at the discharge station under the influence of areverse fluidpressure.

More particularly this invention relates to a wire discharge mechanismfor removing or discharging relatively thin, highly adherent cakes froma filter of the character above described.

The economic Operation of an industrial filter depends among otherfactors upon the ability to cleanly discharge all solids depositedthereon during the so-callcd pick-up period. Although numerous devicesare variously resorted to for this purpose, depending upon the characterof the cake formed on the filter cell, there has been developed to datenomeans for effectively discharging relatively thin highly adherentcakes such as formed, for example, during the filtration of magnesiumhydroxide.

In general, the object of this invention is the provision, inconjunction with a filter 'of the type above described, of a dischargemechanism comprising a pair of. spaced parallel cords maintainedresiliently under tension parallel with the surface of /the filter cellat the discharge station and in the path of the cake carried by thefilter cell or ells.

A fu ther object of the invention is the provision of means operating onthe first of said parallel cords for resiliently opposing the outwardflexure of said cord due to the infiuence of the outwardflexure of thefilter medium carried by said cell when it is placed under the action ofan outwardly directed reverse fluid pressure or blowback. i i

Still another object of this invention is the provision, in conjunctionwith a continuous rotary filter, of roller guides operating on thefilter surface for resiliently maintaining the first of said pair ofcords in contact with the drum surfaceirrespective of the fact that saiddrum may be out of round The invention possesses other advantageousfeatures, some of which with the foregoing will beset forth at length inthe following description, where that form of the invention which hasbeen selected for illustration in the drawings accompanying and forminga part of the present specification is outlined in full. In saiddrawings, one form of the invention is shown, but it is to be understoodthat it is not limited to such form, since the invention as set forth inthe claims may be embodied ina plurality of forms.

Referring to the drawings: 9 Figure 1 is an end elevation of acontinuous rotan drum filter embodying the objects of our invention.

Figure 2 is an enlarged fragmentary section of the filter drum shown inFigure 1, and taken on the plane indicated on the section line 2-2 ofFigure 4.

Figure 3 is an enlarged detailed end, view of the filter shown in Figure1, better illustrating the construction of the mechanism for supportingour plural wire discharge.

Figure 4 is a front elevation of the structure shown in Figure 3, viewedin the plane indicated by the section line ,44 of Figure 3.

Figure MS a fragmentary section taken on the plane indicated by thesection line 5--5 of Figure 2.

Figure 6 is an end elevation of one of the guide rollers shown inFigures 1, 3 and 4.

Figure 7 is a fragmentary section taken on the plane indicated by thesection line i--'l of Figure 6.

For purposes of illustration, our invention has been shown in the abovefigures in conjunction with a continuous rotary drum filter of thevacuum type comprising pedestals ll supporting a filter tankl2,including'tank heads l3. Arranged to rotate within the tank I2 is afilter drum it formed with drum heads l5 and supported in the usualfashion by trunnions journaled in bearings carried by the tank heads l3.

' In accordance with standard practice, there is keyed to one of thedrum trunnions a ring gear 16, disposed in a gear housing l6- -A, andthrough which the drum isdriven by an electric motor II, a suitablespeed reducer l8 and a worm l9.

tending division strips 24, in part defining a series 9 of contiguousfiltrate compartments or cells 25. The open side of each of thesefiltrate compartments or cells 25 is closed by a flexible filler dium 26(which may, for example, be made of cotton duck or twill) secured Withinchannels formed in the'division strips 24, and in the drum heads I 5 bycalking strips 21 or any other suitable means. Disposed within each ofthe filtrate compartments 24 is a coarse drainage screen 28, andoverlying each of these screens for the purpose of serving as a supportfor the filter medium 26 is a wire mesh supporting screen 29.Communication between each of the filtrate compartments or cells and theautomaticvalve 2| is established by means of piping 3|.

The filter as so far described is of conventional construction, such as,for example, resorted to in i the continuous rotary drum filters ofOliver United Filters Incorporated.

Adjustably bolted to a portion of the tank head structure 32 at eitherend of the tankis a bracket 33 provided with a web 34, extendingsomewhat forward of the surface of revolution generated by each of thefiltrate compartments 2-5. Threaded through openings formed in the web34 are upper and lower, eye bolts 35 and 36, to which are threaded oneither side of the web 34, locknuts 31 and 38. Secured to each of theupper eye bolts35 is a tension spring 39; and secured to the inner endsof these springs and held thereby respaced points along the drum surfaceis prevented by threading the rope 43 through the ends of inwardlextending fingers 56,, adjustably secured to the brackets 45 beneath therods 46. Adjustment of the fingers 56 to and from the filter drum maybeeffected by forming slots in these fingers, and securing them to thebracket 45 by bolts or machine screws '51 threaded through the slots.

Due to the difference in the function of the rope 43 from that of thefunction of the Wire 4| (presently tobe explained), there is nonecessity for resiliently holding the rope 43 against the drum at spacedpoints thereon.

Each of the filtrate compartments or cells 25, defined in part byadjacent division stripsopposed drum heads and the filter medium 26secured to these members, may be considered as individual filter panels.If a band is placed over the drum intermediate the ends of any one ofthe filtrate compartments, this compartment may be considered as havingbeen divided by the band siliently under tension across the face of thefilter drum, in the path of the oncoming cake, is a section 4| of pianowire. Similarly secured to the lower eye bolts 36 are tension springs42, and secured to the inner ends of these springs immediatelyacross theface of the drum is a inch diameter cord or rope 43;. The brackets 33are adjustably secured to the tank head portions 1 inner end of the rod46 is an eye 41 in alignment woth the piano wire 4| and through whichthe piano wire is threaded. Fastened to-each of therods 46,intermediate. the filter drum and the bracket 45, b means of a set screw48, is a collar 49, and compressed between this collar and the bracket45 is a coil spring 5|, urgingthe collar 49 and the. rod 46 inwardly,and consequently serving to oppose the outward 'fiexure of the pianowire 4| at this point.

With the construction so far described, the inner ends ofjthe'rods 46,through which the piano wire 4I'is threaded, would ride on the surfaceof the filter medium, thereby subjecting the filter medium to unduewear. To avoid such wear, there is secured over the filter drum in. theplane of each of the rods 46 a metal band 52, and the collar 49 isprovided with a pair of up-standing cars '53, to which is journaled aroller 54, in rolling contact with its associated band 52.

Under certain condtionsthe bands 52, although tightly secured over the,filter drum, are subject to some lateral creepage, and to avoid this,the sides of the rollers 54 areformed with small flanges 55, whichstraddle the band, and thereby serve to maintain the band in alignmentwith its associated roller (see Figures Band '7).

Outward flexure of the cord or rope 43 at into twoindependentpanelsdisposed end to end, and an filter involving this type of construction,may be referred to as a panel type filter. As each of these panelsarrives at a point opposite the discharge stationthat is, opposite thepiano wire-4| and the cord 43-it is subjectedto an outwardly directedreverse fluid'pressure or blowback for the purpose of somewhat looseningthe cake58 carried by its filter medium, Upon the application of thisblow-back, the section of fiexible filter medium associated with eachpanel is outwardly flexed into pillow form, as shown in Figure 5. Thefunctionof the piano wire 4| is to ,lift the cake "58 away from thefilter medium, and

this can be effectivel accomplished onlyif the wire is made to conformas closely as possible at all times during the discharge periodto thepillow form of each of the panels being discharged. It is forthis reasonthat the outward flexure of the :piano wire 4| is resiliently opposed bythe compression springs 5| at points opposite the ends of each of thepanels. Although the piano Wire 4| serves to lift the cake from itsfilter medium, once the cake has passed over the piano wire, contrary toexpectation, it tends immediately to re-adhere to the filter medium,this action takingplace even though the discharge station is below thehorizontal centerline .ofthe drum as shown in Figure 2. The function ofthe rope or cord 43 is, therefore, to wipe from the filter medium thecake which has passed over the piano wire, and which has re-adheredsomewhat to the drum. From this point on, the cake falls by gravity fromthe rope or cord 43; In

this connection, it should be kept in mind that the wire dischargemechanism above described is particularly advantageous in dischargingrelatively thin, sticky cakes, and that there would be noparticularreason for resorting-to this type of discharge mechanism fordischarging relatively non-adherent cakes.

For thefiltration of magnesium hydroxide on a continuous rotary drumvacuum filter of the character abovedescribed, it has been founddesirable to top feed the filter by means of a weir 59, provided with adepending lip 6|. The magnesium hydroxide slurry is then fed to, theweir 59 (as well as to the tank |'2) from which it flows over the lip 6|to the drum at the zenith of the drum. However, the specific method offeeding the filter and forming the cake thereon .is immaterial to thepresent invention. a

We claim:

1. In a. filter wherein a filter panel provided with a flexible filtermedium travels in a closed path through a body of material to befiltered under the action of an inwardly directed difierential filteringpressure, so as to pick up acake on said filter medium, and wherein saidfilter panel is subjected to an outwardly directed reverse pressure at adischarge station for aiding in the discharge of said cake; means forfurther aiding the discharge of said cake comprising: a pair of spacedparallel cords disposed normally parallel with the surface generated bysaid filter panel, and in the path of the cake carried thereby; meansfor maintaining said cords under tension; and additional means forresiliently restraining the first of said cords at spaced points thereonfrom being outwardly flexed, due to theoutward flexing of said filtermedium when said filter panel is subjected to said reverse pressure. Y

2. In a filter wherein a filter panel provided with a flexible filtermedium travels in a closed path through a body of material to befiltered under the action of an inwardly directed difierential filteringpressure, so as to pick up a cake on said filter medium, and whereinsaid filter panel is subjected to an outwardly directed reverse pressureat a discharge station for aiding in the discharge of said cake; meansfor further aiding the discharge of said cake comprising: a pair ofspaced parallel cords disposed normally parallel with the surfacegenerated by said filter panel and in the path oi the cake carriedthereby; means for maintaining said cords resiliently under tension; andadditional means acting at right angles to the first 01' said cords andat the ends oi. said filter panel for resiliently opposing the outwardfiexure of said first cord in response to the outward fiexure oi saidfilter medium when said filter panel is subjected to said reversepressure;

3. In a filter wherein a filter cell, to the marsinal edges of which issecured a flexible filter parallel cords located adjacent to andnormally parallel with the surface of said filter cell at said dischargestation and in the path of the cake carried on said cell; means formaintaining said cords under tension; and additional means forresiliently opposing any outward flexure of said first cord at the ends01' said cell, due tothe outward fiexure of said filter medium when saidflexe said filter medium in outwardly convex pillow form: means fordischarging said cake from said filter medium comprising first andsecond spaced parallel cords located at said discharge station normallyparallel with said cell and in the path of the cake carried by itsfilter medium; means for resiliently maintaining said cords undertension; and additional means operating on said first cord at rightangles "thereto, and opposite the ends of said cell for resilientlyopposing the outward fiexure of said first cord under the influence ofthe outward fiexure of said filter medium.

5. A continuous filter comprising: a filter tank; a filter drum arrangedto'rotate within said tank and provided on its periphery with aplurality of longitudinally extending filtrate compartments over each ofwhich is secured a flexible filter medium; means for successivelysubjecting each of said compartments to an inwardly directed filteringpressure and to an outwardly directed reverse pressure for successivelyurging the filter medium associated with each of said filtratecompartments to assume an outwardly convex form; a pair of spacedparallel wires supported by said tank across and immediately adjacentthe face of said filter drum on the descending side thereof; means formaintaining said wires under tension; longitudinally spaced wireretainers supported by said tank and associated with the upper one ofsaid spaced parallel wires for restraining said wire from movingoutwardly in response to the pressure exerted by the filter mediumsecured to said drum.

each of said filtrate compartments; and means for resiliently urgingsaid wire retainerstoward 6. A continuous filter comprising: a filtertank; a. filter drum arranged to rotate within said tank and provided onits periphery with a plurality of longitudinally extending filtratecompartments over each otwhich is secured a flexible filter medium,means for successively subjecting each of said compartment to aninwardly directed filtering pressure and ,to an outwardly directedreverse pressure for successively urging-the filter ported by said tankand associated with the upper one 01 said spaced parallel wires forrestraining cell is subjected to the action oi. said reverse fluid withthe consequent formation on said filter medium of a layer of cake, andwherein said cell upon approaching said discharge station is subieetedto a reverse fluid pressure for loosening said cake from said filtermedium, and which said wire from moving outwardly in response to thepressure exerted by the filter medium secured to each of said filtratecompartments; means for resiliently urging said wire retainers towardsaid drum: and rollers carried by said wire retainers arranged toride onthe cylindrical surface of said filter drum.

'7. A discharger for rotary drum filters comprising: a wire held undertensionimmediately adjacent and substantially parallel to the axis ofthe drum of said filter; and means intermediate the ends of said wirefor resiliently restraining it from flexing outwardly in response to anyoutward fiexure oi the filter medium carried by said filter drum.

- EDWIN LE'I'I'S OLIVER.

PHILIP J. MOGUIRE. JAMEB E. SLAUGHTER.

